Stents are devices used for inserting in a vessel or other part, employed in many cases to provide support for or prevent collapse of parts such as blood vessels. In specific cases, for example, stents are placed within arteries that have become dangerously narrow or during surgeries related to overcome blockages. Stent applications are not limited to blood vessels but include also parts such as ureters, bile ducts, and bronchi. Currently, stents are made of corrosion resistant metals such as titanium-nickel alloys and stainless steel. These stents may need in some cases to be removed, which requires a secondary intervention into the body.
Due to this problem of necessary removal, there are continuous efforts to manufacture biodegradable stents that can be absorbed in the body. This would provide significant advantages such as decreasing immune responses to non-endogenous materials and avoid a secondary, invasive procedure for removal of the stent. Polymer biodegradable stents for cardiovascular applications based on poly (D, L-lactic-co-glycolic acid) (PLGA) and poly (D, L-lactic acid) (PLA), polyglycolic acid (PGA) are known in the art. However, these stents are not equal to non-degradable metal stents in terms of mechanical properties.
Biodegradable magnesium implants attract significant attention because of certain advantages they offer compared to conventional metal implants. Magnesium corrodes in the body thus allowing elimination of a second surgery to remove the implant. The main approach to controlling magnesium properties is based on doping and alloying with a variety of different elements. Lately, magnesium based biodegradable stents for temporary scaffolding of coronary arteries have been introduced.
Major efforts related to stent manufacturing are focused on engraving the stent configuration. Currently, this operation employs laser cutting of a stent tube, followed by polishing, since the laser beam evaporates material that partly deposits on the surface of the stent. This approach is expensive and the productivity is low. The latter is related to the scanning speed of the laser that processes the stents one by one. Another approach is braiding of wire made of the stent material. Braiding has some advantages for making of magnesium stents that helps in overcoming the low elasticity of this metal. This approach requires a great amount of thin magnesium wire with a diameter of a couple hundred microns to be fed into the braiding machine. Currently, magnesium wire is available on the market from only a few vendors offering limited diameters and at very high prices. In addition, the low tensile strength of the magnesium wire demands redesigning of the available micro-braiders and modifying their mechanics in a way that they do not break the wire during braiding.
Methods of making and using biodegradable magnesium stents are herein described that overcome the long-felt needs of high-quality, reliable biodegradable stents and overcome specific problems described above.